It's true, better to have the ara of low pressure in the manifold after the port than an area of high pressure in the port before the manifold. always make the exhaust port slightly smaller than the entrance to the manifold.
cool , thought it made sense tbh! im currently working thro as much info as i can find b4 i start the porting, will update after the weekend thanks all
DONT reduce the short side radius ! Take another look at the Popular hotrodding link to see why. Good luck with the project.
Those valve seats look well recessed into the head. You're probably getting a lot of restriction from the step between the seat and combustion chamber at low valve openings.
yep, tho the vavles are sitting about 1mm proud when fully closed. think ill get the valves reseated, would that sort it??
Willie, could you take some more pics of the ports and post them up please? just going by what i can see up there getting more flow out of that head could be done with a small file, lol. Those ports are p*sh.
Cheers, can you take some more, straight into the ports and from both sides please. The pics should come out clearer if you take them under a light and switch your cameras flash off. Sorry to be a rectal pain
no problem pls bear in mind my digicam is about 18yrs old and held together by gaffer tape, pretty much like my car btw! is that better......
You need to smooth off that step so it flows cleanly. Having new inserts to lift the valve up will cost about 100 per 4 valves, so not really worth the money... Ideally you'd machine back the whole combustion chamber area to take it out, and then have the head skimmed to bring the chamber volume back, but if you're working with a dremel or similar, then just smooth off the step.
45 degree edge on the step all the way round. Hold a valve in 1mm open, see what effect you think the valve seat/comb chamber step has. Air flow at low valve lift is really important. All material removed from inside the combustion chamber will reduce CR. On performance heads the part of the combustion chamber between the valves is a point, like an upturned V, blended into the seat and right into the port.
Fine sandpaper, start about 400grit, wet, then work up in stages to as high a grit as you can get hold of. This is a CPU waterblock i lapped to 1200grit on a sheet of glass to make it flat, no extra polishing has been done. *edit* holy mother of TSC! an blind infant with a toy file could improve the flow from that head willie! Those are some of the worst ports i have seen tbh, no wonder the 8v VW's are under preformers! My bet, and i would put money on this, is that even a first time porter who has done some research could get 10 hp out of that head, just with a mild clean up and very slight port reprofile. That things shockingly bad.
that was on a real nice early 5door , slammed, kn filters, full scorpion zorst, that got tattered nr my house and i got for 80 im glad u feel the same way about the potential, tis why im getting as much info b4 i start! keep em coming guys more ideas the merrier, edit.... fair enuff about 8v vws but would just like to mention my mk1 cabbie, totally standard bar kn filter and bit of tinkering ,got well off the clock a few weeks ago.
Any clearer pics or the inlet ports bud ? What are you using to grind the ports ? Looks like something low-speed, though could just be the pics.
